Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the lingual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars.
Mature calculus consist of an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to bone, enamel and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris and various types of microorganisms.
As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. This is undesirable from an aesthetic standpoint.
A wide variety of chemical and biological agents have been suggested in the art to retard calculus formation or to remove calculus after it is formed. Mechanical removal of this material periodically by the dentist is, of course, routine dental office procedure.
The chemical approach to calculus inhibition generally involves chelation of calcium ion and/or crystal growth inhibition which prevents the calculus from forming and/or breaks down mature calculus by removing calcium.
The prior art discloses a number of chelating agents for this purpose. British Patent 490,384, Feb. 15, 1937, discloses oral compositions containing ethylenediaminetetraacetic acid, nitrilotriacetic acid and related compounds as anticalculus agents. U.S. Pat. No. 3,678,154, July 18, 1972 to Widder et al. discloses oral compositions containing certain polyphosphonates and fluoride. U.S. Pat. No. 3,737,533, June 5, 1973 to Francis discloses oral compositions containing certain carbonyl diphosphonates.
In addition to the use of the above mentioned materials, the use of certain polymers and other agents have also been disclosed for use as anticalculus agents. Included among such agents are polyelectrolytes such as copolymers of maleic anhydride and ethylene disclosed in U.S. Pat. No. 3,429,963, Feb. 25, 1969 to Shedlovsky. Shedlovsky also discloses polyacrylic acid having an average molecular weight of 1500 and greater. Other references disclosing polymeric polycarboxylic acids in oral compositions are South African Patent 720898, Sept. 12, 1972 which discloses such polymers having a molecular weight of from 1000 to 2,000,000; and U.S. Pat. No. 4,304,766, Dec. 8, 1971 to Chang discloses polyacrylic acid having a molecular weight in the range of 2,000 to 4,000,000 for use as a membrane to prevent the elution from teeth of previously applied agents. Finally U.S. Pat. No. 3,956,480, May 11, 1976 to Dichter discloses complexes of anionic polymers (e.g., acrylic acid) and a cationic therapeutic agent (e.g., chlorhexidine) as anticalculus agents.
In spite of the many disclosures in the anticalculus area, the need for improved products and methods still exist. The present invention is directed to the recognition that stannous ions when complexed with certain carboxylic acids or polyhydric alcohols provide anticalculus efficacy.
It is an object of the present invention therefore to provide methods for reducing calculus.
It is a further object of the present invention to provide methods utilizing stannous ions.
These and other objects will become clearer from the detailed description which follows.
All percentages and ratios used herein are by weight of the total composition unless otherwise specified. Additionally, all measurements are made at 25.degree. C. in the composition or in an aqueous solution/dispersion unless otherwise specified.